Prior to actual printing of sheet material, dust and other dirt particles deposit on the sheet to be printed, particularly if the sheet is electrostatically charged by friction or other influences. The sheet is typically paper, but may also include other materials or be coated with aluminum or plastic, for example. Such dirt particles impair the quality of the printing and decrease the life expectancy of the backing cloths (rubber cloths) and the printing mechanism as well.
Known apparatuses for cleaning the sheet before it is printed in the printing mechanism consist of suction nozzles, which vacuum the dirt particles from both sides of the sheet. It is also possible to use brushes for brushing off the sheet. Both known possibilities have the disadvantage of scratching the surface of the sheet, and causing the fibers of the sheets to be upright. These upright fibers are then torn off in the printing mechanism and adversely affect the backing cloth and the quality of the printing.